1. Field of the Invention:
This invention relates to the inspection and separation of geometrically symmetrical stable units such as buttons, and more particularly to the inspection of the central zone of such units for defects and the automatic separation of the defective buttons for acceptable buttons.
2. Description of the Prior Art:
When a button is manufactured, threadholes, or eyes, are placed in the central zone of the button. Every button manufactured does not have the holes or eyes formed so perfectly that the button can be used on a garment. For example, the holes may be partially closed, improperly spaced, or missing entirely. In addition, since buttons are generally now sewn on garments by automatic machinery, the defective hole pattern can cause a break-down of the machinery with the resulting down-time causing a loss of productivity. Therefore, buttom makers have been required to inspect buttons after manufacture to insure that those sold to garment manufacturers meet commercial standards. To the present time, most buttons are inspected by the human eye as the buttons pass on conveyor belts before the workers charged with the task. Visual inspection has proven to be necessarily tedious work and an ineffecient method of inspection.
Various schemes have been proposed for the automatic inspection and separation of buttons. One such scheme is shown in U.S. Pat. No. 3,956,636. Another, employing laser technology and computers, has also been proposed. The initial cost and the problems of maintenance of such a high technology system make it of doubtful commercial practicality. A third system is shown in U.S. Pat. No. 4,196,811. While this third system has proved accurate and efficient, calibration problems arose because each button must move at a predetermined velocity and be exposed to the light source for a predetermined time. The need for frequent calibration has detracted from the commercial viability of this system.
Accordingly, it is an object of the present invention to provide an economical and reliable method and apparatus for the inspection and separation of buttons which does not require frequent calibration or precision in velocity and spacing, thereby eliminating the need for the presence of a skilled technician during the inspection process.